SLA or DLP 3D Printing? How to choose between them.

For many industry insiders and hobbyists, 3D Printing has become a household name. However, the technology used in DLP (Digital Light Processing) or Stereolithography (SLA) printers is still relatively unknown to most people. In this article we would like to help you understand the differences, to make a choice between SLA or DLP.

Stereolithography process schematic

UV hardened printing

Stereolithography uses a UV laser to scan and cure a photosensitive resin liquid which builds an object up one layer at a time.

A DLP printer uses a projector that shines onto a pool of resin which then hardens each layer one at a time. Layer 1 will be semi-hard while layer 2 just below is hardened further. This allows for each layer to “fuse” and harden with the previous layer creating a more homogeneous material.

An SLA printer acts more like an FDM (Fused Deposition Modelling), curing the resin in a “tool path” while the DLP does an entire layer at once. Both the DLP and SLA printers have less visible layers than an FDM one will produce, use photo-polymers, and create high resolution parts.

Choosing SLA or DLP

While both DLP and Stereolithography printers will typically be more accurate than their FDM counterpart, other considerations need to be made when evaluating printers. The light source in a DLP printer can be very easily replaced, just like a projector, unlike an SLA printer which requires a laser which is more expensive to replace.

In addition, a DLP printer has the ability to control the light source and its effect on the resin as a variable. An SLA printer’s light is fixed and can’t be modified without changing the laser.

Another factor is the maturity of the technologies. 3D Systems has been playing with Stereolithography since the 1980’s whilst DLP is a much newer technology.

Finally, users should keep in mind that the main money-maker for these companies is the consumable. When selecting between the two options, the user should factor in the pricing and usage of the resin required for each technology.